1. Field of the Invention
This invention relates to marking devices and more particularly, to intermittent motion transfer tape imprinters.
2. Prior Art
Imprint markers are commonly used in industry for various purposes including applying last minute information to product packaging, such as code dating, net weight, price and the like information which cannot advantageously be applied to the packaging at time of the original printing of the packaging.
Such marking devices generally fall into one of three categories: (1) ink devices such as those using stamp pads or ink rollers; (2) inked tape devices; and (3) transfer tape devices. This invention is particularly directed to transfer tape devices wherein the tape, sometimes referred to as a foil, is coated with a pigmentation which, under application of heat from a heated marker head, will cause transference of the pigment to the product to be marked.
Intermittent marking devices using transfer tape have two peculiar requirements not found in other marking devices. These are (1) necessity of complete withdrawal of the head from the tape and (2) complete advancement of the tape. The first requirement arises due to the fact that the head is normally heated so that the raised indicia which represent the marking to be applied to the product are kept at an elevated temperature. Since marking is intermittent, it is necessary for the head to be raised entirely out of contact with the tape except during the imprinting operation. This requires a relatively long stroke. Generally an anvil is positioned opposite the head, the product is passed over the anvil, the tape is positioned between the head and the product and either the head or the anvil is moved so as to bring the heated head into contact with the tape and the tape into secure contact with the product such that the tape and product are compressed between the head and the anvil.
For various reasons, it is sometimes preferable that the head move rather than the anvil. In this type of construction, the head must necessarily undergo a relatively large amount of movement towards and away from the anvil. Although this movement may be on the order of fractions of an inch, it remains a relatively large amount given the thickness of the transfer tape involved. Thus, in order to provide smear-free imprints, the head must be securely held against sway movements or any movements other than directly towards and away from the anvil.
The second requirement arises due to the nature of the transfer tape. Since the pigment of the tape in the area of the raised indicia of the head is entirely transferred to the product, any restrike of that area of the transfer tape will result in an incomplete imprint. Therefore, it is necessary to completely advance the tape between each strike by the imprint head. Ideally tape advancement is done on the retracting stroke of the marker head.
Recently, it has also become important to reduce the size of such imprinters to produce as compact a design as possible so that the imprinter may be installed on production machinery where relatively little space is provided. Finally, it has become important to allow for quick replacement of the transfer tape, either to change the color of the tape, or, more normally, to allow for quick replenishment of depleted tape rolls.
Numerous linkages and tape drive mechanisms have been suggested in the past. For example, in my U.S. Pat. No. 3,823,664, I employed a pneumatic cylinder which drove a shuttle which had spaced openings therealong. One of the openings engaged a camming member which caused tape advancement whereas the other opening drove one end of a bell crank arm supporting the moving anvil. This use of a common shuttle, both for movement of the anvil and the tape advance mechanism, allowed both functions to be carried out by a single power cylinder as compared to the required usage of two power cylinders to accomplish the separate functions shown, for example, in my U.S. Pat. No. 3,881,410.
A typical one-way clutch system for advancement of tape on the retract stroke of the power cylinder attached to a moving head is illustrated in U.S. Pat. No. 4,160,410 where, however, the head is otherwise freely attached to an end of the power cylinder arm and is merely supported by an underlying support. In my U.S. Pat. No. 4,121,520, I have shown a moving marker head which employs a projecting shaft on the marker head which is held in a sleeve bearing which greatly restricts movement of the marker head thereby insuring a quality imprint. In this latter patent, I provided a slot in the marker head shaft with a pin spanning the slot riding in the groove of an oscillating rocker drive member powered from a power cylinder. Although this construction provides a drive train having certain advantages, the necessity of using a rocking drive link requires that the power cylinder be hinged so as to allow the drive arm of the power cylinder to move both axially and laterally. This type of device, although effectively stabilizing the printing head, required the use of undesirable power transfer linkages, and results in a device having a relatively large axial dimension from the indicia to the point of connection to the power arm.
It would be an advance in the art to provide an imprint marker which provided the advantages of some of the prior art constructions while eliminating some of the disadvantages inherent therewith. Specifically, it would be an advance in the art to provide an intermittent imprint marker, of relatively compact size, wherein the print head is stabilized against sway; where the print head movement thrust is applied axially along the center line of the print head; where tape drive and print head movement are both provided by a single power source; and, where the drive linkage is securely guided having only reciprocal movement.